In secondary batteries, an inorganic material, such as carbon, lithium-cobalt oxide (LiCoO2) or the like, is used as an electrode material. Therefore, no matter how such an inorganic electrode material is made thin, it may be easily cracked and thus destroyed when it is bent, so there is a problem in that it is difficult to apply it to next-generation batteries such as flexible ultrathin batteries and the like.
In order to overcome the above problem, NEC Corporation has developed polymers containing an organic radical. However, most of such polymers have low heat resistance, so there is a problem in that it is difficult to assure the lifespan of secondary batteries.
Recently, a method of stabilizing an organic radical polymer having a polynorbornene structure by curing polymer chains among themselves has been reported. However, this method is problematic in that it is difficult to increase the degree of curing because reactions occur only when polymer chains are in very close proximity to one another, and, particularly, in that, when a conventional inorganic electrode material, such as carbon or the like, is mixed with this organic radical polymer in order to increase an electrode capacitance, there is an increased tendency for polymer chains to keep away from each other.
Therefore, it is keenly required to develop an organic radical polymer electrode active material which can overcome the problem of low density and low conductivity, which does not cause a problem even when it is mixed with other inorganic electrode materials and which can be formed into a thermostable and flexible thin film.